JPS62163571A - Dc-dc converter unit - Google Patents

Abstract

PURPOSE:To compensate the error of the detected voltage by providing a series detection circuit of a diode and a resistance between the emitter of a switching transistor and an input DC power source and by changing the condenser from the base of the above-mentioned switching transistor and detecting the primary winding current. CONSTITUTION:A DC-DC converter unit is composed of a converter transformer 22, a switching transistor (hereinafter referred to as Tr) 23, their control circuit 29, etc. and connects a load ZL between output terminals 35-35' to feed the current. On this occasion, a diode 27 and a condenser 28 are connected to a bias winding n3 and the output voltage is detected. Through a resistance 30 they are added to a control circuit 29 and its output voltage is stabilized by controlling the ON-time of the Tr 23. On the other hand, for the purpose of detecting the input current of a transformer 22, a diode 24 and a resistance 25 are inserted between the Tr 23 and an input terminal 21' and a diode 31 and a condenser 32 are connected to the base of the Tr 23. With the charging voltage the detected voltage of the above-mentioned output voltage impressed to the control circuit 29 is changed and the output voltage is compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a controlled DC-NC converter device, and more particularly to a DC-DC converter device aimed at improving the stability of output voltage.

2. Description of the Related Art Conventionally, this type of DC-DC converter device has had a configuration as shown in FIG. In Fig. 2, 1 is a positive voltage input terminal connected to the positive electrode of the input DC power source E;
' is a negative voltage input terminal, which is connected to the negative voltage of the input DC power source E. 6 is a transformer with a primary winding n1. Output winding n2. Drive winding n3. It has a detection winding n4. 4 is a switching transistor whose collector is connected to the primary winding n1
connect to input terminal 1 through the drive winding n
3f to the input terminal 1', and the emitter is connected to the input terminal 1'. A resistor 5 has one end connected to the input terminal 1 and the other end connected to the base of the switching transistor 4. 9 is a diode whose anode is connected to the input terminal 1' via the detection winding n4, and whose cathode is connected to one end of the capacitor 10 for reading. 1o is a capacitor, the other end of which is connected to input terminal 1'. Reference numeral 11 denotes a control circuit, one end of which is connected to the input terminal 1, the other end of which is connected to the cathode of a diode 90, and the other end of which is connected to the bases of all the switching transistors 4. 2 is an output terminal with a positive potential, 2' is an output terminal with a negative potential, and a load ZL is connected between the output terminals 2 and 2'. 7 is a diode whose anode is connected to the output terminal 2' via the output winding n2i, and whose cathode is connected to the output terminal 2. 8 is a capacitor, one end of which is connected to the output terminal 2, and the other end connected to the output terminal 2'.

Although the operation of the circuit shown in FIG. 2 is well known, an outline thereof will be described below for convenience of explanation.

When the input DC power source E is applied to the input terminal 1-1', a base current flows through the resistor 5 to the base of the switching transistor 4, and as a result, the switching transistor 4
is turned ``on''. An excitation current begins to flow through the primary winding n1 of the transformer 6, but at this time, no current flows to the output winding 02 because the diode 7 has a reverse polarity. Since a positive voltage is generated on the side of the drive winding n3 with respect to the switching transistor 40, a base current flows to ensure the "on" operation of the switching transistor 4.

The "on" period is controlled by the control circuit 11, and there are two methods for controlling it: directly controlling the base current, or controlling the time using a timer circuit. The excitation current of the line n1 increases and stops increasing when it leaves the saturation region of the switching transistor 4, and a reverse voltage is generated in the drive winding n3, causing the switching transistor 4 to increase.
This is done by controlling the base current by taking advantage of the property of the switching transistor 4 to turn "off" rapidly.Alternatively, in the latter case, an off pulse is applied to the base of the switching transistor 4 using a timer circuit or the like to forcefully turn it all "off". do.

When the switching transistor 4 turns "off", the excitation power starts to be released and the voltage of the output winding n2 is reversed.
Diode 7 is passed through capacitor 8 and output terminal 2-2
A current is sent to the load Zt connected to . During this period, a reverse voltage is generated in the drive winding n3, and as a result, the switching transistor 4 remains "'off", but when the excitation power of the transformer 6 is finished discharging, this voltage is reversed again and the switching transistor 4 is turned off. Transistor 4 is turned on. Therefore, the output current stops, and the excitation current starts flowing through the negative winding again. Thereafter, the switching operation will be repeated.

On the other hand, a diode 9 and a capacitor 10 having the same polarity as the output winding n2 are connected to the detection winding n4, thereby detecting the output voltage. The detected voltage is applied to the control circuit 11 described above, and the “ON°
'The output voltage is stabilized by controlling the time.

In this way, in this method, the output detection voltage total detection winding n4
Therefore, it is not possible to detect fluctuations in the output voltage caused by changes in loss in the output circuit due to changes in load current and changes in the waveform relationship between windings due to leakage inductance, and this causes control residuals on the output side. remains as. For this reason, there was a drawback that the output voltage could not be completely stabilized.

FIG. 3 shows a conventional example made to improve the above-mentioned drawbacks. In FIG. 3, the same parts as in FIG. 2 are denoted by the same reference numerals, and explanations thereof will be omitted. 3 is a capacitor, 12 is a resistor, and 13 is a diode.
connected in series. Diode 13 is connected to input terminal 1'
It is connected to the cathode side. capacitor 3 and resistor 1
The connection point 2 is connected to the emitter of the switching transistor 4, one end of the drive winding n3, and one end of the control circuit.The operation of this circuit is the same as the conventional 11tl shown in FIG. A resistor 12 and a diode 13 are provided to detect the input current of the gold capacitor 10, and the voltage across these terminals is used as a detection output for compensation.In addition to the voltage across the gold capacitor 10, that is, the detection output of the output voltage, this combined detection voltage is sent to the control circuit 11.
It is used as input.

The capacitor 3 smoothes the high-frequency pulsed primary winding current and converts it into a direct current.

The voltage across the resistor 12 and the diode 13, ie, the detection output for compensation, must be in a proportional relationship with the load fluctuation characteristics of the output voltage, and this determines the compensation accuracy.

Therefore, it is desirable that the constituent elements be constituted by impedance elements equivalent to the DC operating impedance of the main circuit. This conventional series is an example in which the current detection circuit is composed of a resistor 12 and a diode 13. That is, the resistor 12 corresponds to the sum of the resistance of the output winding n2 and the resistance of the load Zt, and the diode 13 corresponds to the diode 7, respectively.

Next, the improvement effect of this conventional array will be explained with reference to FIG. In the figure, the human curve shows the load fluctuation characteristics before improvement. If the voltage across the resistor 12 and the diode 13, that is, the characteristic when the compensation detection output is converted into an output voltage, is the curve B, then the control gl is performed along the curve B, so the output voltage is equal to A'. The result will be a curve and an improvement will be made.

Problems to be Solved by the Invention In such a conventional configuration, the compensation detection output performs compensation by detecting the input current, which fluctuates in proportion to the output current. Since the output voltage also fluctuates in response to fluctuations in the output voltage, the stability of the output voltage due to fluctuations in the input voltage deteriorates.

Furthermore, since the diode 13 is included in the compensation detection circuit, the forward voltage of the diode 13 has temperature characteristics, so the compensation detection output varies depending on the temperature, and the temperature characteristics of the output voltage deteriorate. Furthermore, since the detection output for correction uses fluctuations in negative voltage, the detection voltage applied to the control circuit 11 requires a positive voltage, and the bias winding and the detection winding cannot be shared. Further, the capacitor 3 has the problem that it is expensive and large in size because a large capacitance capacitor is required in order to smooth the large high frequency pulse current flowing through the primary winding n1.

The present invention solves these problems by correcting errors in detected voltage caused by fluctuations in load current, and making it possible to completely stabilize the output voltage even in the face of input voltage fluctuations and temperature fluctuations. Moreover, the purpose is to construct the circuit with a relatively simple circuit at low cost and in a small size.

Means for Solving the Problems In order to completely solve this problem, the present invention provides a main conversion circuit comprising a switching transistor, a converter transformer, and a rectifying and smoothing circuit connected in cascade between an input DC power source and a load. and a control circuit that controls the on/off duty ratio of the switching circuit by inputting the detection voltage of the output voltage obtained from the detection winding provided in the converter transformer, and completely stabilizes the load voltage. In order to detect the primary winding current, a series detection circuit including a diode and a resistor is provided between the emitter of the switching transistor and the input DC power supply, and the base of the switching transistor is connected to the input DC power supply via the diode. A detection voltage of the primary winding current is charged in a capacitor, and a current proportional to the detection voltage of the primary winding current is applied to the detection voltage of the output voltage from a series circuit of a resistor and a transistor connected across the capacitor. It is configured as follows.

Effect: With this configuration, errors in the detected voltage due to fluctuations in the load current are compensated for, and the output voltage is completely stabilized.

Embodiment FIG. 1 is a circuit configuration diagram of a DC-DC converter device according to an embodiment of the present invention. In FIG. 1, 21 is a positive voltage input terminal connected to the positive electrode of the input DC power supply Z. ,
21' is a negative voltage input terminal, which is connected to the negative voltage of the input DC power source E. 22 is a converter transformer with a primary winding n1. Output winding n2. It has a drive winding n3f. 2
3 is a switching transistor whose collector is connected to the input terminal 21 through the primary winding n1, whose base is connected to the input terminal 21' through the drive winding n3i, and whose emitter is connected through a series circuit of a diode 24 and a resistor 25. and is connected to the input terminal 21'. The diode 24 is connected so that the cand is on the input terminal 21' side. A resistor 26 has one end connected to the input terminal 21 and the other end connected to the base of the switching transistor 23. 2. Connect the cathode to the base of the switching transistor 23 with a diode, and connect the anode to the input terminal 21 via the capacitor 28.
′. 29 is a control circuit with one end connected to transistor 2
3, the other end is connected to the input terminal 21', and the other end is connected to the connection point between the diode 27 and the capacitor 28 via a resistor 3o.

31 is a diode whose anode is connected to the base of the transistor 23, and whose cathode is a total capacitor? 32 to the input terminal 21'. 33 is a transistor (PNP
), the emitter is connected to the connection point between the diode 31 and the capacitor 32 via the resistor 34, and the base is connected to the input terminal 21'.
The collector is connected to the connection point between the control circuit 29 and the resistor 30. 35 is a positive potential output terminal, 36' is a negative potential output terminal, and a load ZL is connected between 35 and 35'. 36 is a diode whose anode is the output winding n2
The cand is connected to the output terminal 35' through the terminal 35'. A capacitor 37 has one end connected to the output terminal 35 and the other end connected to the output terminal 35'.

The circuit operation of FIG. 1 is the same as that of the conventional series shown in FIGS. 2 and 3, but the output voltage is detected in a reverse polarity operational relationship with the output winding n2 connected to the bias winding n3. A diode 27 and a capacitor 28 are connected and this negative voltage is used. The detected voltage is the control circuit 2
9 through a resistor of 3° to control the output voltage and stabilize the output voltage. On the other hand, the converter transformer 2
In order to detect the input current of 2, the voltage generated across a series circuit of a diode 24 and a resistor 25 connected between the emitter of the switching transistor 23 and the input terminal 21' is applied from the base of the switching transistor 23 via the diode 31. applied to capacitor 32. The voltage applied to the capacitor 32 forward biases the transistor 33 through the resistor 34, so a current proportional to the voltage applied to the capacitor 32 flows through the collector of the transistor 33 to the resistor 3o, increasing the voltage across the resistor 30. changes,
The detection voltage of the output voltage applied to the control circuit 29 is changed. The change in the detection voltage of the output voltage is caused by the capacitor 3
Increasing or decreasing the voltage across the converter transformer 220
When the input current increases or decreases, it acts to increase or decrease the detection voltage of the output voltage applied to the control circuit 29, thereby compensating the output voltage.

Therefore, the amount of compensation is resistance 25. Resistance 34. A wide range of compensation is possible by adjusting one or more values of the resistor 3o, and it is possible to accurately compensate for the output voltage that changes depending on the DC impedance of the main circuit.

Effects of the Invention As described above, according to the present invention, the peak value of the input current of the converter transformer, that is, the high-frequency pulse current, is detected by a diode and a resistor, and the capacitor is peak-charged from the base of the switching transistor via the diode. Compensation is being provided. Since the peak value of the high-frequency pulse current is hardly affected by the input voltage and varies only by the output current, extremely stable compensation for input fluctuations is possible.

Furthermore, regarding temperature characteristics, the diodes cancel each other, and the switching transistor's base and emitter and the transistor's emitter and base cancel each other, so the temperature stability with respect to the amount of compensation is very good. Furthermore, all the components required for compensation can be made up of small components with low capacitance, and the detection winding and bias winding can be shared, resulting in an inexpensive configuration suitable for high-density packaging and miniaturization. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a DC-DC converter device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional DC-DC converter device, and FIG. 3 is a circuit diagram of a second conventional column. , FIG. 4 is a characteristic diagram of the second conventional column. E...Input DC power supply, 21.21'...
Input terminal, 22...Converter transformer, 23
...Switching transistor, 24...
・Diode, 25... Resistor, 26... Resistor, 27... Diode, 28... Capacitor, 29... Control circuit, 30...・Resistor, 31...Diode, 32...Capacitor, 33...Transistor, 34...
・Resistance, 35°35'... Output terminal, 36...
...Diode, 37...Capacitor. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Diagram transition

Claims (1)

[Claims] A main conversion circuit consisting of a switching transistor, a converter transformer, and a rectifier and smoothing circuit connected in cascade between an input DC power source and a load, and a detection voltage of an output voltage obtained from a detection winding provided in the converter transformer. The emitter of the switching transistor and the input include a control circuit that controls the on/off duty ratio of the switching circuit and stabilizes the load voltage as an input, and detects the primary winding current of the converter transformer. A series detection circuit consisting of a diode and a resistor is provided between the DC power supplies, and a detection voltage of the primary winding current is charged to a capacitor connected to the input DC power supply from the base of the switching transistor via the diode, and a detection voltage of the primary winding current is applied to both ends of the capacitor. A DC-DC converter device characterized in that a series circuit of a resistor and a transistor connected adds a current proportional to a detected voltage of the primary winding current to the detected voltage of the output voltage.